Reciprocating drilling tool



United States Patent Oflice 3,384,190 Patented May 21, 1968 Crumbo Filed Nov. 14, 1966, Ser. No. 593,978 9 Claims. (Cl. 175-293) The purpose of this invention is to provide a drilling tool capable of faster, more economical drilling of hard formations, as in oil or gas well drilling by the rotary method, wherein a fluid is used to circulate cuttings to the surface.

Hard (e.g. rocky) formations are diflicult to drill through with the rotary grinding action provided by conventional drill bits by the rotary method. This invention provides a drilling tool equipped with a plurality of drill bits capable of a reciprocatory, hammer-like, chipping action which fractures such formations more effectively. These drill bits form part of the tool, which, nevertheless, is mounted at the end of a conventionally-designed rotary drill string, rotational movement thereof being translated into consecutive reciprocatory action of the drill bits by cam means devised according to the invention, actuable upon contact with the formation encountered, and without the need of special controls connected to the well platform.

More specifically, the tool of the invention consists of a housing carrying a central hollow drill shaft or mandrellike member which constantly rotates with the drill string, and constantly drills what may be termed a guide-hole. Rotationally mounted around said mandrel or drill shaft is a cam member capable of actuating a plurality of reciprocating drill bits circumferentially arranged around said mandrel, which are brought into action when a resistant formation is met, the latter bits being so mounted with respect to the cam means that rotary motion of the shaft member is translated into reciprocatory action of the plural bits against the bore-hole formation.

Special port means are provided to circulate fluid flow through the mandrel, through the exterior of said reciprocating bits, and thence exteriorly up past the tool to the well head.

Further features of the invention will be understood from a description of the drawing, wherein:

FIG. 1 is an elevation of the bottom of the tool;

FIG. 2 is a vertical section taken on lines 2-2 of FIG. 1, and FIG. 3 is a sectional detail of the cam member 20.

The tool, generally indicated at it includes a housing 11 having a central threaded bore at its top 12, for attachment to the end of a drill string (not shown). Housing 11 also has a hollow or sleeve-like member or portion 13 in which the remaining parts are housed.

The central drilling member 14 is pipe-shaped for most of its length and at its top is threadedly connected to housing 11 for passage of drilling fluid pumped down through the drill string and bore 12. The lower portion 15 of member 14 is of more solid constuction in order to carry drill teeth 16, and is connected to member 14 at screw threads 27 for easy removal. Portion 15 is provided with fluid exit ports 17.

A disc-type cam is splined to the central member 14 at 21 and rotates therewith, cam 20 being capable of relative vertical movement. A relief spring 22 is interposed between the top of cam 20 and the internal face of housing 11 to prevent the cam 20 from overloading the mechanism operated by it, about to be described. Cam 20 carries a depending flange 23 sinuously curved in such manner to provide (in the example given) four relatively projecting portions 24, each equally separated by four relatively indented portions 25 (FIG. 3). These flange portions 24-25 provide the camming action for the reciprocating drill bits 30 next to be described.

In the example given in the drawing, there are peripherally arranged around and adjacent to the portion 15 of member 14 eight wedge-shaped reciprocating bits 30, together substantially forming a complete circle around members 14-15. Each bit 30 has Wedge-shaped teeth 31 on the lower face opposite the formation to be drilled and carries on the outer periphery the laterally protruding teeth 32 for shaping and reaming the borehole. Four slots 33 are provided (FIG. 1) between bits 30 to allow for fluid circulation back to the surface exteriorly of the tool, as seen in FIG. 1. Only one solt 33 can be seen in FIG. 1.

Each reciprocating bit 30 is affixed to a reciprocating drive rod 35, the latter passing through spaced bores in a sleeve-like rod holder or guide 36, the latter being journaled for rotation relative to member 14 and housing 11 by means of a plurality of bearings 37. Each drive rod is provided with a cap 38 containing a ball-bearing 39 for engagement with surfaces 24-25 of cam 20, being urged into contact by return springs 40 located between caps 38 and the upper face of guide 36. Due to the sectioning of FIG. 2, four of such drive rod assemblies are seen therein, there being altogether eight, one for each bit 30.

0perati0n.When the tool is lowered by a rotating drill string through relatively soft formations, teeth 16 of central drilling member 14 act like a drill bit, constantly drilling a guide hole. When a relatively hard formation is encountered, at least half of the eight drill bits will be in extended position and will engage the formation. This engagement will prevent any substantial further rotation of the bits 30, guide 36 and drive rods 35. Since cam 20 will continue to rotate along with member 14, the cam surfaces 24-25 will activate drive rods 35, forcing bits 30 to reciprocate in an alternate fashion. By this means, because at least some of the bits 30 are always extended and in engagement with the formation, continuance of the reciprocation of the bits is achieved as long as the formation presents enough resistance. However, if desired, the bits 30 can be made to rotate relatively slowly by decreasing the weight of the drill string upon the tool. Drilling fluid pumped down member 14 exits at ports 17 and carries cuttings through slots 33, thence to the surface, externally of the tool.

What is claimed is:

1. In a drilling tool, in combination, a tool housing having means for attachment to a conventional string of drill pipe for use in a rotary earth boring operation of a drill hole; a depending elongated hollow member centrally attached to said housing for rotational movement therewith; a cam member mounted on said hollow member for rotational movement therewith; a plurality of reciprocatory drill bits axially mounted with respect to said hollow member in a manner to permit relative non-rotation of said bits with respect to said hollow member, and connecting means between said cam member and said drill bits producing a reciprocating drilling action by said drill bits whenever said bits encounter a resistant formation in said drill hole.

2. The invention according to claim 1, wherein said cam member consists of a ring-shaped cam mounted around said hollow member for rotary movement therewith, said cam having spaced projections in contact with said connecting means providing a sequential reciprocatory action by said drill bits.

3. The invention according to claim 1, wherein said rill bits are each provided with peripheral laterally protruding teeth for reaming the drill hole.

4. The invention according to claim 1, wherein said tool housing and said hollow member are connected to said string of drill pipe by a hollow connection allowing for passage of drilling fluid through said hollow member to the formation encountered by said drill bits.

5. The invention according to claim 4, wherein said hollow member has a lower portion provided with drill teeth and exit ports therethrough for passage of said drilling fluid.

6. The invention according to claim 1, wherein said connecting means includes a sleeve journaled around said hollow member, and drive rods carried in said sleeve, each rod being connected to a reciprocatory drill bit, said drive rods being in spaced apart contact With said cam member.

7. The invention according to claim 6, there being a relief spring interposed between said sleeve and said tool housing.

8. The invention according to claim 1, wherein said drill bits are pie-shaped and together substantially form 4 a ring of separately operated bits around said hollow member.

9. The invention according to claim 8, wherein ports are provided between said bits for the exit of drilling fluid.

References Cited UNITED STATES PATENTS CHARLES E. OCONNELL, Primary Examiner.

R. E. FAVREAU, Assistant Examiner. 

1. IN A DRILLING TOOL, IN COMBINATION, A TOOL HOUSING HAVING MEANS FOR ATTACHMENT TO A CONVENTIONAL STRING OF DRILL PIPE FOR USE IN A ROTARY EARTH BORING OPERATION OF A DRILL HOLE; A DEPENDING ELONGATED HOLLOW MEMBER CENTRALLY ATTACHED TO SAID HOUSING FOR ROTATIONAL MOVEMENT THEREWITH; A CAM MEMBER MOUNTED ON SAID HOLLOW MEMBER FOR ROTATIONAL MOVEMENT THEREWITH; A PLURALITY OF RECIPROCATORY DRILL BITS AXIALLY MOUNTED WITH RESPECT TO SAID HOLLOW MEMBER IN A MANNER TO PERMIT RELATIVE NON-ROTATION OF SAID BITS WITH RESPECT TO SAID HOLLOW MEMBER, AND CONNECTING MEANS BETWEEN SAID CAM MEMBER AND SAID DRILL BITS PRODUCING A RECIPROCATING DRILLING ACTION BY SAID DRILL BITS WHENEVER SAID BITS ENCOUNTER A RESISTANT FORMATION IN SAID DRILL HOLE. 